We all have bad days - it's just a fact of life. You practice and practice for an audition. You nail it when you're at home in front of your video camera and feel like you have this one in the bag. But then you get into the audition room and it all goes exactly opposite of what you expected.
After the audition, you beat yourself up mercilessly. You replay what went wrong... how you could have done it differently. The self-loathing and second-guessing goes on and on in a continuous loop in your brain, blowing it way out of proportion. Right?
Take professional athletes for example. They train consistently but it doesn't guarantee that they won't have bad days too. They could win a gold medal one day, and then come in 5th the next day. As one of my favorite books, "The Four Agreements," says, 'Always do your best. Your best is going to change moment to moment. It will be different when you are healthy as opposed to sick. Under any circumstance, simply do your best, and you will avoid self-judgment, self-abuse and regret.'
So when you have a bad audition, let it go. Don't beat yourself up - what good does that do really? Hopefully the casting director sees something in you to bring you back another time. We know that people have bad days, but it's about how you recover from those days and move forward. If you're going to pursue an on-camera career, you have to accept it and quickly learn how not to let it defeat you and your dreams.